Worst condition indicating system



12 Sheets-Sheet l J. W. SADVARY ETAL woHsT CONDITION INDICATING SYSTEM April 19, 1966 Filed Aug. 25, 1962 ISIDOR T. FLAUM mw mf April 19, 1966 J. w. sADvARY ETAL 3,247,498

WORST CONDITION INDICATING SYSTEM FIG. 2

INVENTORS JOH N W SADVARY MICHAEL POCHTAR ISIDOR T. FLAUM April 19, 1966 .1. w. sADvARY ETAL 3,247,498

WORST CONDITION IDIGATING SYSTEM 12 Sheets-Sheet 5 Filed Aug. 23. 1962 V ccgf E? QT j: C EC DDB CCC:

April 19, 1966 .1. w. sADvARY ETAL 3,247,498

WORST CONDITION INDICATING SYSTEM Filed Aug. 25, 1962 12 Sheets-Sheet 4.

99E/7 J0 7/0 JCO/V INVENTORS JOHN W. SADVARY 3 MICHAEL POCHTAR |S|DOR T. FLAUM By weowa New April 19, 1966 J. w. sADvARY ETAL 3,247,498

WORST CONDITION INDICATING SYSTEM 12 Sheets-Sheet 5 Filed Aug. 25, 1962 077' 01 IVE y April 19, 1966 J, w, SADVARY ETAL 3,247,498

WORST CONDITION INDICATING SYSTEM Filed Aug. 23, `1962 12 Sheets-Sheet 7 my N GQ I @NR IlmA Q. d. *Imm HITGA/Ey April 19, 1966 J. W. SADVARY ETAL WORST CONDITION INDIGATING SYSTEM 12 Sheets-Sheet 8 Filed Aug. 23, 1962 FAB wwwwiu 6g rh f3 -9 s S y 4i 5l l 5 e, 36a 22 la 353 s 7 5 Q R l 9 INVENTORJ JOHN W. SADVARY ISIDOR T. FLAUM April 19, 1966 J. w. sADvARY ETAL 3,247,498

WORST CONDITION INDICATING SYSTEM Filed Aug. 23, 1962 12 Sheets-Sheet 10 MICHAEL POCHTAR FIG. ISIDOR T. FLAUM April 19, 1966 J. W. SADVARY ETAL.

WORST CONDITION INDICATING SYSTEM Filed Aug. 23, 1962 12 Sheets-Sheet 11 INVENTORS JOHN W. SADVARY MICHAEL POCHTAR ISIDOR T. FLAUM QM 912mm 12 Sheets-Sheet 12 J. W. SADVARY ETAL WORST CONDITION INDICATING SYSTEM April 19, 1966 Filed Aug. 23,

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. www P Sg MM y Y 5 Mmmm N mVCL R EAP o# V s L T NHD JM QPS United States Patent O 3,247,498 WORST CONDITION INDICATING SYSTEM John W. Sadvary, Garfield, Michael Pochtar, Livingston,

and Isidor 'I'. Flaurn, Hasbrouck Heights, NJ., assignors to The Bendix Corporation, Teterboro, NJ., a corporation of Delaware Filed Aug. 23, 1962,'Ser. No. 218,070 19 Claims. (Cl. 340-213) The invention relates generally to performance indicators and more particularly to indicators for indicating the perfomance of several devices.

As the speed of modern aircraft increased, aircraft instruments also increased in number and complexity to the point where the pilot can not comfortably or effectively monitor the instruments in the time available. As an example, the DC-6 has 423 instruments, controls, switches, and warning lights; whereas the later DC-S has 638 such devices. y

The increasing number of indicators reflects the increasing complexity of modern aircraft. Moreover, these complex aircraft must be operated at optimum performance parameters. As an example, consider fuel consumption as a function of speed. In a DC-S turbo-fan, a change in speed from an optimum of .82 Mach for certain flight conditions, to .84 Mach, a change of 2.4 percent, increases the fuel consumption disproportionally by l2 percent.

As aircraft become faster and still more complex, the number of instruments will tend to increase, optimum operating parameters will become more critical, and the time available to the pilot and crew to monitor the instruments will be further shortened.

One object of the invention is to provide a novel indicator system for several devices which displays the performance parameters of the worst performing devices.

Another object of the invention is to provide a novel indicator system for indicating a malfunction in any one of several devices.

Another object of the invention is to provide a warning signal when the parameter of two devices differ from one another by more than a predetermined amount.

Another object of the invention is to provide a novel indicator system for use with several devices which cornputes and displays the optimum value or range of values at which the devices should operate, and the limit values beyond which the devices should not operate.

Another object of the invention is to provide a novel indicator system for monitoring a plurality of performance parameters of several devices and which displays the parameters of the worst performing devices.

Another object of the invention is to provide a novel indicator system for monitoring a plurality of performance parameters of several devices by indicating which v devices, if any, are malfunctioning.

Another object of the invention is to provide a novel indicator system for monitoring a plurality of devices and providing a warning signal when two like parameters of different devices differ from one another by more than a predetermined amount.

Another object of the invention is to provide a novel indicator system, for monitoring a plurality of performance parameters of several devices and which displays indicator means connected to the performance meansand to the signal means for displaying the performance parameter of the worst performing device. The indicator system also contemplates means for comparing each parameter signal to a reference and providing a malfunction signal when the parameter signal departs from the reference a predetermined amount. The system also contemplates means for providing a warning signal when two parameters differ from one another a predetermined amount. The indicator system also contemplates means for computing and displaying the optimum value or range of values at which the devices should be operating and the limit values beyond which the devices should not be operated.

The system also contemplates means for determining the above signal and'value for a single parameter and for a plurality of parameters of several devices.

The foregoing and other objects and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description which follows, taken together with the accompanying drawings wherein one embodiment ofthe invention is illustrated by way of eX- ample. It is to be expressly understood, however, that the drawings are for illustration purposes only and are not to be construed as defining the limits of the invention.

In the drawings:

FIGURE 1 is a block diagram of an indicator system constructed in accordance with the invention.

FIGURE 2 is a schematic drawing showing in detail part of the timing device shown in FIGURE l.

FIGURE 2A is a graph illustrating one complete timing sequence.

FIGURE 3 is a graph Showing representative timing signalsused to sequence the performance section in the computing section shown in FIGURE l.

FIGURE 4 is a schematic drawing of the performance section in the computing section of FIGURE 1.

FIGURE 5 is a schematic drawing ofthe diode memory in the computing section of FIGURE 1.

FIGURE 6 shows a portion of the performance section of FIGURE 4 to assist in explaining the operations of the section.

FIGURE 7 is a schematic drawing showing in detail the engine Adisplay transfer of the performance section shown in FIGURES 4 and 6.

FIGURE 8 is a schematic drawing of part of the Nixie drive circuit of the performance section shown in FIG- URES 4 and 6.

FIGURE 9 is a schematic drawing showing in part the output engine display of the performance section shown in FIGURE 4.

FIGURE 10 is a schematic drawing of the performance monitor of the computing section of FIGURE 1.

FIGURE 11 is a schematic drawing of the Prop low RPM energizing block of the performance section of FIGURE 4.

FIGURE 12 is a schematic drawing of the performance look-up memory of the computer section shown in FIG- URE 1.

Referring to the drawings and particularly to FIG- URE 1, the novel indicator system constructed in accordance with the invention receives three types of input signals, namely, analog signals Q, PE, Fp, %RPM, To, WF, TIT from the four engines'which are called the performance parameter signals, signals Qc (velocity), Hp (altitude) from an air data computer called ight condition signals, and signals K2 through K5 indicating engine throttle position called command signals.

The indicator system provides five types ofV output signals to a display panel 22 in the cockpit (1) signals proportional to the actual operating conditions of the worst Patented Apr. 19, 1966- performing engine, (2) signals indicating a malfunction, (3) warning signals when two engines operation differs from each other by more than a predetermined amount, (4) greenline signals indicating the optimum operating value or range of value for a particular parameter, and (5) redline signals indicating unsafe limits or unsafe ranges of operation.

Analog signals, oil quantity Q, engine oil pressure PE, oil cooler flap position Fp, percent revolutions per minute %RPM, oil temperature To, fuel flow WF, and turbine inlet .temperature TIT, proportional to the performance parameters of each of the four engines, are applied to an input switch 2 along with the signals Qm'Hp from the air data computer. Input switch 2 sequentially supplies the signals to an analog to digital converter 4 which converts the analog signals to binary digital signals. The digital signals are applied to a computing section y6 including a performance section 10, a diode memory 12, a performance monitor 14, and a look-up memory i6.

Performance section 19 of computing section 6 determines for each performance parameter which engine is the worst performing. Section 1t) controls an output switch 20 which receives analog signals Q, PE, Fp, %R'PM, To, WF, TIT through a multiple bus 21 to connect the input signal proportional to the worst performing engine to an indicator in display panel 22. It should be noted that the displayed signal is applied directly through switch 20 to display panel 22.

Computing section 6 also provides signals indicating malfunctions for each parameter in each engine and activates a bank of Nixie bulbs 24 in the display panel 22 to indicate the malfunction by engine number and parameter.

Computing section 6 also provides t0 display panel 22 redline signals indicating maximum and/ or minimum safe ranges for certain parameters.

Computing section 6 also provides signals to display panel 22 indicating optimum performance values or ranges for certain parameters.

A power supply 26 and timing block 28 energizes and synchronizes the system.

The analog performance parameter signals may be provided by sensors (not shown) within the engines of any convenient or conventional types and the signals are converted to digital form by analog to digital converter 4.

The signals applied to input switch 2 preferably are 400 cycle per second sinusoids having a phase that varies from a reference in accordance with the parameter. For certain parameters, the most reliable sensors presently available do not provide a 400 c.p.s. variable phase signal and devices may have to be included between the sensor and converter 4 to convert the signals as sensed to phase variable 400 c.p.s. signals.

Input switch 2 sequentially' connects the parameter signals to analog to digital converter 4. Each signal is connected for a duration of four cycles. The rst cycle permits the settling of transients, and the analog to digital conversion is performed during the second cycle. Switch 2 may be of any convenient or conventional type, for example, electromechanical, diode switching matrix, or gating or of a novel type shown and described in April 18, 1963, U.S. patent application Ser. No. 273,994, assigned to the same assignee as the present application.

Analog to digital converter 4 converts the phase varying signal to a proportional binary pulse train. Converter 4 is of a type that receives a reference signal and the phase displaced signal with the amount of phase displacement from the reference is proportional to the analog quantity sensed. The positive zero crossing of the reference signals initiates a square waveform and the positive or negative zero crossing of the phase displaced signal terminates the square waveform. The square waveform that is generated partially qualifies a gate that also receives a high frequency pulse train from a clock i to pass a number of clock pulses into a counter while the square waveform is generated.

This type of analog to digital converter is well known and is generally explained in Susskind, Notes on Analog- Digital Conversion Techniques, 1957, New York, John Wiley, cf. p. 6-8 ff. A particular circuit for generating the square Waveform is shown in Carrozza and Nashelsky, application Ser. No. 173,720, assigned tothe same assignee as the present application.

The converter 4 itself may be of any other convenient or conventional type, for example, of the kind shown and described in Masel and Blauvelt, application Ser. No. 176,304, assigned to the same assignee as the present application.

If digital sensors are used, converter 4 may be dispensed with, and the sensed parameter signals in digital form from switch 2 can be applied directly to computing section 6.

TIMING The timing and synchronizing of the system is provided by timing block 2S including two two-stage counters 32, 36 and matrixes 34 and 37 respectively, a three-stage counter 38 and a matrix 39 shown schematically in FIG- URE 2.

A 400 c.p.s. reference signal is applied to a fiip-flop 31 0f two-stage cycle counter 32. .Flip-flop 31 halves the frequency of the 400 c.p.s. signal and provides alternate high and low signals at the outputs 31S and 31K. Output 31R' is connected to a second flip-hop 33 which halves the frequency of the 200 c.p.s. signal from flip-flop 31 and provides alternate high and low signals at outposts 33S and 33K. Outputs of flip-flops 31 and 33 are connected to diode matrix 34 which provides sequentially on output terminals 34a, 34h, 34C, and 34d high signals corresponding to rst, second, third, and fourth cycles of the 400 c.p.s. reference.` Output 34h is connected to analog to digital converterv 4 and energizes the converter to perform the analog to digital conversion during the second cycle.

A second two-stage counter 36 is connected to output 34d and has flip-Hops 36A and 36B connected to a diode matrix 37 and is identical to counter 32 just described. The second or Engine counter 36 and matrix 37 keeps track of which engine is being monitored, by providing a high signal on outputs 37a, 37b, 37C, and 37d of matx 37 corresponding respectively to engines 1, 2, 3, and 4. The signals on outputs 37a, 37b, 37a and 37d are designated El, E2, E3 and E4, respectively. Outputs 37a, 37b, 37C and 37d are connected to input switch 2 and signals E1, E2, E3 and E4 energize the switchA to advance the switch to receive the parameter signal of the next engine.

A three-stage flip-Hop counter 38 similar in design to the counters just described, and a diode matrix 39 analogous to the diode matrixes just described is connected to output 37d and sequentially provides high signals on outputs 39a through 39h corresponding to the parameter being sensed. The signals available at these outputs are designated P1 through P8, respectively.

If input switch 2 is of the gating type, an output from the engine matrix 37 and from the parameter matrix 39 may be used to activate the appropriate gate. The eight parameter cycles P1 through P8 constitute a timing sequence that lasts for, and is repeated each, 320 milli-` seconds.

There is shown in FIGURE 2A a graph illustrating one complete timing sequence. This is made up of eight P timing periods of 40 milliseconds each. Each P timing interval is, in turn, subdivided into four E timing intervals designated E1 through E4, each of which is 10 milliseconds. The E timing period has four 400 c.p.s. reference cycles, each cycle occupying 2.5 milliseconds. During the rst .64 millisecond of each third reference cycle, there is a further series of timing signals called the performance section timing sequence shown in the graph of signal is available during intervals 2 through 8. Likewise y With timing signals TZ, T3, etc., E, etc. t TS and Each timing interval may include an a timing signal which indicates a high pulse-'at the beginning of the timing interval, and may include a d timing signal indicating a high pulse at the middle of the timing interval, and may include an e timing signal indicating a high pulse at the end of the timing interval. Timing signals a, d, or e have subscripts thereto indicating in which major timing interval it is available. For example, if a conductor receives signals d1, d2, d4 through d8, the pulses applied would be of the type shown in graph 3. There is also available a converse of the a, d, and e signals. These represent a high signal at all times except a low pulse for that period of time designated by the timing signal, for example, in the graph of FIGURE 3, there is shown an 53 pulse and an E8 pulse applied on a signal conductor and El through E8 timing signal applied on a signal conductor.

Also available are bundles of shift pulses, bearing the legends b1 through bg. Each bundle comprises ten low pulses and is supplied during the time interval indicated by the subscript.

Parameter signals P1 through P8 from parameter ma! trix 39 and .engine signals E1` through E4 from engine matrix 37 are also used in the performance section 10, indicating which parameter is being sequenced. Signals P1 through P8 indicate a high for the duration of the parameter designated by the postscript. A converse signal, for example, P S, indicates a high signal for the duration of all parameters other than parameter P3 during which time there is a low signal. Likewise, for the engine signals E1 through E4, and their conversesignals through l PERFORMANCE SECTION Performance section is shown in the schematic drawing of FIGURE 4 and includes a 10 bit counter and shift register A of the kind that counts pulses applied on conductor 7 and registers pulses applied on conductor 9. Performance section 10 includes three l0 bit registers N, P and R of any conventional or convenient type adapted to receive pulses both in series and in parallel, and give up these pulses when activated by the b pulse train shown in FIGURE 3. Registers N and P are set to 1 or reset to O upon application of a negative-going pulse at set and reset terminals S 'and R, respectively.

A plurality of Nand gates are included and shown in performance section 10. These gates have a high output when any input is low and a low output when all inputs are high.

A gate G3 receives a square waveform from analog to digital converter 4 and clock pulses from look-up memory block 16 to drive the register A. Gate G5 receives b1 to ba signals and shifts the contents of the A register around on itself. A gate G6 receives a T5 timing signal from Vthe output of the N register shifting the contents of the N register around on itself during each T5 timing interval. A gate G9 receives the output of the P register and a timing signal T1 and is connected to the N register to transfer the contents of the P register to the N register during the T1 timing interval. A gate G10 receives the output of the P register and the T5 timing signal and transfers the contents of the P register around on itself for all timing intervals except T3. A pair of gates G12 and G13 have their outputs connected to the P register and both receive the T3 timing signal and receive, respectively, 'FF-3' signal and F133 signal and receive, respectively, the output from P register and the output from the A register to transfer during the third timing interval the contents of the A register into the P register or the contents of the P register around on itself in accordance with the FF3 or m signals. A gate G14 receives P6, E4, and T4 timing signals as well as the output from P register to transfer the contents of the P register during the coincidence of the P6, E4, and T4 timing signals. A gate G15 receives the output of the R register and T5 timing signals and transfers the output of the R register around on itself during the T5 timing signal.V

Gates G21 and G23 are connected, respectively, to the set and reset terminals S and R of register P, and gates G22 and G28 are connected to the set terminal S of register N for filling these registers with 1s and O's. Gate G21 passes a signal to the S terminal upon the coincidence of P1 or P2 and an al and E1 timing signals. Gate G23 passes an energizing signal to reset terminal R upon the coincidence of El and a1 timing signals during either P3, P4, P5, P6 or P8 timing periods. Gate G22 passes a signal to the set S terminal of register N upon the coincidence of the aflor ag pulse during either the P1 or P6 timing period; and gate G28 passes apulse to the set terminal upon the coincidence of an a8 signal during the P2 or P3 timing intervals.

, l0-that is part of an interrogating subunit 41.

A gate G27 receives a P6 timing signal and a 55 pulse train which shift the contents of the R register during the fifth timing interval of the P6 timing period.

The outputs of the A and N registers are applied directly to and through inverters 57 and 58 to comparator Interrogating subunit 41 has two Hip-flops' 50 and 53 having set S and reset R input terminals that are activated by negative-going signals to provide a high signal at the. corresponding outputterminals S' and R. Flip-flop 50 is set by the 5.6 signal or by a signal from a gate G24 that is activated by an al pulse during the P3 through P8 timing intervals. Flip-Hop 50 is reset upon the application of a E3 or E3 signal. Comparator 40 and flip-flop 50 are connected to gates G25' and G26 that are also partly qualified by timing signals d1, d2, d4 through d8 to energize set input of flip-flop 53. Flip-flop S3 provides FF3 and signals mentioned above. These signals also energize display transfer 60 and output engine display 80. The F123 signal energizes a Nixie bulb circuit 59 through a gate G29 and flip-ilop 55. The FFSsignal passes through gate G29 when it is coincident with an e8 signal to set ip-op 55 and provide a signal on a conductor to the Nixie bulb circuit 59. The EP3 signal also partially qualies a gate G31 which is also partially qualified by a P4 and a5 signal. This gate G31 provides a 94 percent low signal to performance monitor 14. The F133 signal also energizesa prop low RPM block 90. Y

An output from comparator 40 is also connected to a gate G which is partially qualified by P6 and E7 timing signals. Output from this gate -is applied through an inverter 107 providing signal to performance monitor 14 dealing with oil temperature.

The structure and operation of the comparator 40 and interrogating subunit 41 are examined in detail after which the entire performance section is examined both as to structure and operation.

C-omparator 40 may be of any'convenient or conventional type having the following characteristics: Two signals to be compared from the A and N registers designated A and N and their converse and are applied to comparator 40 which initially is placed in a condition to make a comparison by a reset pulse applied on a conductor 46. The comparator has two outputs 47 and V48. A high signal is provided on output 47 when A is less than N (A N), a high is provided on output 48 when A is greater than N (A N), and both conductors 47 and 48 are low when A is equal to N (A=N). A comparator having these characteristics is shown andV described in Thomas and Weiss U.S. patent application Serial No. 219,204, assigned to the same assignee as the present application.

Outputs 47 and 48 are connected respectively to two gates G25 and G26. These gates also receive signals respectively from the set S' and reset R outputs of an interrogating flip-flop Sti and timing signals d1, d2, d., through d8. Gates G25 and G26 are connected to energize the set input S of an answering fiip-iiop 53. This flip-flop provides a signal FF3 high when the set input S is energized and a signal m high when its reset R is energized. Answering flip-flop 53 is reset upon the application of a negative-going pulse applied to its reset terminal through a conductor 54.

The two gates G25 and G26, and two flip-flops 50 and 53 cooperate with comparator 40 forming what may be termed an interrogating subunit 41 considering the interrogating subunit 41 as a whole, an interrogating signal is applied to the set S input of iiip-op 50 via conductor 51 if the unit is looking for A greater than N; and an interrogating signal is applied to reset terminal R via conduetor 52 if the unit is looking for A less than N. A reply to the interrogation signal appears at the output of iiipflp 53 and is either yes or no Yes is indicated by a high on the set output S of iiip-tiop 53 and is designated by FFS high signal. No is indicated by a high on the reset output R of flip-flop 53 and is designated by a m high signal.

The interrogating signal applied to ip-fiop Sti (i.e. looking for A greater than N, or A less than N) is determined by the particular comparison being made, and in turn, is determined by the parameter and the contents of the A and N register.

Diode memory 12, performance monitor 14, and lockup memory 16 cooperate with performance section 10 to determine the worst performing engine and malfunction of engines. Diode memory 12 provides minimum and maximum malfunction limits to `the N register. Diode memory 12 is shown in detail in schematic drawing in FIGURE 5 and is of conventional type.

Performance monitor 14 determines the acceptance limits in accordance with command signals. Look-up memory 16 provides variable malfunction reference signals and optimum values, and in this embodiment is used only for one parameter.

The performance section can be best described by considering its operation for each parameter. n The parameter requiring the least computation is oil quantity and is designated parameter P1. Performance section 16 determines which of the four engines has the minimum oil quantity to activate output switch'20 so that an oil quantity indicator in the cockpit displays the quantity of oil in that engine. Also, performance section 1t) provides a malfunction signal to Nixie bulb indicator 24 in the cockpit causing a bulb to display the number of those engines whose oil quantity is less than four gallons.

The necessary computations are performed in timing interval T1, T2, T3, T6, and T8. The remaining time intervals are used for those parameters requiring more computations. It should be noted that the performance section goes through all the T1 through TS steps, although the steps T4, T5, and T7 do not produce any useful information for this parameter.

The necessary computations are performed by using only the A, N, and P registers. The R register is not used for this parameter. Also, lonly gates G3, G5, G12 and G13 are used for this parameter.

The performance section is redrawn in FIGURE 6 showing only those parts, and indicating only those signais, that are used and provide useful information for the oil quantity parameter. The operation of the per-` formance section for this parameter can be more easily followed with the aid of this simplified .drawing and the simplified explanation that follows. The complete set of steps performed by the performance section to be used in conjunction with the drawing of FIGURE 4 is set down in outline form directly after the simplified discussion.

During the second reference cycle of the first engine E-l of the first parameter P-l, the engines performance as to oil quantity is gated into the A register through gate G3 by the square waveform from converter 4 prior to the operation of the performance section.

During the first timing interval T-l, gate G21 activated by signals E1 and a1 fills the P register with 1s. In response to the b1 pulse train signal, the contents to the A register are shifted around on itself through gate G5; and the contents of the P register are transferred to the N register through gate G.

During the second time interval; the E2 pulse applied on conductor 46 resets comparator 40, (The interrogating fiip-tiop 56 has previously been reset to look for A less ythan N.) In response to the b2 pulse train, the contents of the A-and N registers are shifted directly and through inverters 57 and SS into comparator 49. At the same time, the contents of the A register are shifted around on itself through gate GS. The d2 timing signal is applied to gates G25 and G26 and if the A is less than N, gate G26 passes a signal to set iiip-fiop 53 producing a FF3 high signal.

During the third timing interval T3, the b3 pulse train is applied to the A register to shift its contents around on itself via gate G5. When A is less than N, by the interrogation just performed, the contents of the A register are gated to the P register via gate G13 enabled by FF3 and T3. It should be noted that for the first engine A is always less than N as the N register contains a maximuninumber, i.e. all ls. When A is greater than N, i.e. FF3 is high, the contents of the P register are shifted around on itself through gate G12. The next timing pulse d3 activates engine display transfer 69, shown in detail in the schematic drawing of FIGURE 7.

Engine display transfer 66 shown schematically in FiG- URE 7 utilizes the outputs from engine counter hip-flops 36A and 36B. These outputs designated 36a, @l and 36!) and 3 (5 are applied respectively to Naud gate G61 through G64. Each of gates G61 through G64 also receives through a gate G65 the answering signal FF3 from fiip-lop 53 upon the coincidence of FF3 high and timing signal d3. Gates G61 and G62 have their outputs connected respectively to set S and reset R inputs of a flip-flop 66; and gates G63 and G64 have their output connected respectively to set S and reset R inputs of iiipop 67. These flip-flops temporarily store the worst performing engine number. Outputs from iiip-iiops 66 and 67 available on conductors 68 and 69 indicate in binary code which engine is the worst performing. The code is shown in the lower portion of FIGURE 7, a O designating a low signal and a l designating a high signal.

After the fourth engine performance has been considered, the engine number in engine display transfer 60 is transferred to output engine display 89 as shown in FIGURE 4. Display St) stores this number and activates output switching matrix 20 until the P1 parameter is again considered by computing section 6.

Referring now to both FIGURES 6 and 7, the third timing pulse d3 and the FFS high signal, activates gate G65 and partially qualifies gates G61 to G64. Engine coun-ter iiip-iiops 36A and 36B qualify gates G62 and G64, resetting both flip-Hops 66 and 67 and rendering a 0 "0 output on conductors 68 and 69, which outputs designate engine 1, as the temporarily worst performing engine.

Timing interv-als T4 and T5 for this parameter are only used in connection with .the fourth engine as lis described below.

During timing interval T6, the first engines oil quantity is compared against the malfunction limit, in this case,

four gallons. Parameter `signal P1 and timing signal as applied `to gate G41 in the diode memory 12 shown in FIGURE 6, causes the' N register to register the malfunction limit. The be pulses shift the contents of the A register a number (proportional to the quantity of oil in engine 1) and the contents of the N register (a number proportional to four gallons) into compara-tor 40.

Also during the be pulse train, the contents of ythe A register are shifted around on itself through gate G5; A comparison is made looking for A less than N and if A is less than N in response to a transfer pulse de applied to gate G26, flip-flop 53 is set, i.e. and a FF3 high signal indicates a malfunction in engine 1.

The seventh ltiming cycle T7 performs no computations for this parameter.

In the eighth timing cycle T8, timing signal e8 and answering signal FFS from Hip-flop 53 are yapplied Ito a gate G29. (Signal FFS is high if there is a malfunction.)

Gate G29 sets ya flip-flop 55 that in turn energizes a Nix-ie bulb malfunction circuit 59. This circuit is shown in part in FIGURE 8 `and contains 32 gates, each of which corresponds to -a differentv engine for a different parameter. Each gate receives la parameter signal and an engine signal and output from FFSS. FPhe gates for parameter P1 Iare shown Iand designated G71 through G74. A low output from any of the lgates energizes a Nixie bulb drive circuit (not shown) .that causes the appropriate Nixie bulb and number to light up. The numberis illuminated :for an interval of 12%00 of a second, i.e. until the same engine is again .compared as to malfunction Afor the same paramelter in the sampling cycle.

After the eighth timing cycle T8 i.e. when the performauce section has completed its operation for engine oil quantity for the -rst engine there is stored in the P register .a digital number proportional to the iirst engine oil quantity. If this quantity of oil is less than four gallons, the ANixie bulb corresponding to oil quantity has illuminated thereon the numeral 1.

rPhe oil quantity of engine E2 is next considered. In-

put switch 2 applies a signal corresponding to .the oil quantity of engine E2 .to analog -to digital converter 4. During the second reference cycle, analog to digital converter 4 enters a digital number proportional rto the oil quantity of engine 2 into -the A register. During the third reference cycle, performance section compares .the number in the A register with the number at the P register (i.e. the oil quantity in engines 2 4and 1 is compared). The smaller of the two numbers is stored in 'the P register, and the larger is discarded.

During the third timing interval T3, a d3 signal activates the engine display transfer ygates and, if the quant-ity of oil in engine 2 is less than the quantity of oil in engine 1, the FFS signal -is high and :gate G65 (FIG. 7) passes a signal so ythat iiip-lop 66 is activated to change state.

During the sixth timing interval T6, the oil quantity of engine 2 is compared with the four gallon limit. If engine 2 has less than four gallons, the oil quant-ity parameter Nixie bulbs number 2 is illuminated. This bulb and number are selected during the eighth timing cycle by the coincidence of a FFS high signal and an e8 signal applied to gate G29 that sets iiip-op 55, that -in turn provides a high to Nixie circuit S9 on conductor 7S. In

. NiXie circuit v59, only gate G72 4is partially qualiiied by t-he P-1, E-2 timing signals. 'Ilhe high 4from ip-iiop 55 on conductor 75 fully qualifies only gate G72, activating -Nixie drive circuit (not shown) and illuminates numeral 2 .inthe Parameter 1 -Nixie bulb.

Likewise, for the remaining two engines, the performance section 10 repeats the same steps to determine ythe worst performing engine, and if there is a malfunction, illuminates an appropriate Nixie bulb number.

'Ilhere -is set down below in detailed outline form `the steps performed by the performance section in determining the oil quantity measurements. lead to any useful information for the oil quantity pa- Certain steps do not i rameter, but are included herein because they are neces sary Vfor other parameters. 'Ihe performance section goes through all the steps shown in the outline once Ifor each of the four engines in the outline, and .the steps are repeated four times, oncefor each of Ithe four engines.

Parameter 1 OIL QUANTITY T1 r11-Reset comparator 40, El on conductor 46 (Load SR. P with 1s on engine 1) gate G21 b1-(Compare SR. A with SR. N. Answer must be No.sa) Shift contents of SR. P into SR. N via gate G9 Shift SR. A around on'itself via gate GS Shift SR. P around on itself via gate G10 d1-(Set flipdlop 53 if answer to comparison is YEs'!) el-Reset dip-flop 53 and ip-op S5 (El on conduc tors 54) z2-Reset comparator 40 (E2 on conductor 46) bz-Compare SR. A with SR. N looking for A N.

Shift SR. A around on itself Via gate G5 Shift SR. P around on itself via gate G10 dz-Set flip-flop 53 if answer to comparison is YES d2 to gate G26 a3-Reset comparator 40 E3 on conductor 46 bB-If nip-flop 53 has been set, shift contents of SR. A

' into SR. P via gate G13 If hip-dop 53 has not been set, shift SR. P around on itself vi-a gate G12 Shift SR. A around on itself via gate G5 da-(Reset dip-flop 50 for A N E3 on 52) If dip-Hop 5-3 has been set, transfer engine number infomation into storage hip-flops 66 and 67 -via gate G65 FIGURE 7 z3-Reset ip-op 53 and Hip-Hop 55 (E3 on conductor 54) r4-Reset comparator 40 '64 on conductor 46 [nr-(Compare SR. A with SR. N. Answer must be No.n) Shift SR. A around on itself via gate G5 Shift SR. P around on itself vi-a gate G10 dg-(Set flip-flop 53 if answer to comparison is csYESu) e4-On Engine 4, provide pulse to gate G87 FIGURE 9 to clear output matrix 86 z5-Reset comparator 4.0 55 on conductor 46 On engine 4, provide pulse to gate G83 of FIG- URE 9 to transfer worst case engine information b-(Cfgiar SR. A with SR N. Answer must be Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 d5-(Set ip-cp 53 if answer to comparison is YES.), zy-Reset comparator 40 E6 on conductor 46 Load SR. N with Para. 1 lower malfunction limit via gate G41, diode memory 12 FIGURE 5 bg-Gompare SR. A with SR. N looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 ds-Set Hip-flop 53 if answer to comparison is YES via gate G26 eG-Set flip-flop 50 for A N E6 on conductor 52 aq-Reset comparator 40 '67 on conductor 46 l Load SR. N with 1s gate G22 .bfage SR. A with SR. N. Answer must be Shift SR. A around on itself via .gate G5 Shift SR. P around on itself via gate G10 dT-(Set flip-Hop 53 if answer to comparison is iYES-) 1 l T8 :z8-Reset comparator 40 E8 on conductor 46 Load SR. N with ls via gate G22 11B-(Compare SR. A with SR. N. Answer must be Shift SR. P around on itself via -gate G10 dB-(Set yflip-flop if answer to comparison is YES.) eaSet flip-flop 55 if flip-flop 53 is set via gate G29 (malfunction indication.) Reset flip-flop 53 for A N E8 on conductor 52 In the outline, there is provided -an e4 signal yand an a5 signal that are used only during the fourth E4 engine cycle. The a signal transfers the engine number of the worst performing engine temporarily stored in ip-cps 66 and 67 to a permanent ou-tpu-t engine display Si), shown in part in lthe schematic drawing of FIGURE 9. Output circuit 30 directly activates output switch 20 to transfer the analog signal of the worst performing engine to a suitable indicator device in the cockpit.

Output engine display 80 has seven output units, one for each parameter, but in FIGURE 9 only the unit for the P1 parameter is shown completely with legend. Tlhe remaining six units are of identical structure but have different input and output connections.

The P1 output uni-t :has a pair of input gates G81 and G82 which receive a P1 signal and a timing signal .from a gate G83 through an inver-ter 83 upon the coincidence of an E4 signal with an a5 signal. Gates G81 and G82 receive outputs from flip-flops 66 and 67 respectively. Outputs from gates G81 `and G82 are applied respectively to set inputs S of flip-liops 84 and S5, thus the coded engine number stored in `flop-Hops 65 and 67 of engine display transfer 60 is transferred .to ip-iiops 84 and 85 by tim-ing pulse a5 during the fourth engine cycle. A diode matrix 86 connected to the output S land R of flip-flops 84 and 85 `decodes the engine number and provides a high signal on one of lfour matrix output conductors 86a, Sb, 86C, or 86d indicating the Worst performing engine. These conductors energize output switch 2G. The e4 timing signal coincident with the E4 engine signal and P1 parameter signal energize a Naud gate G87 to reset ipops 84 and 85 and clear matrix 86 just prior to the transferring timing signal from gate G83.

The second parameter P2 -is engine oil pressure and the computations performed by performance section 12 for this parameter are similar [to those performed for oil quantity. The `engine oil pressure in the engine having lowest pressure is displayed in the cockpit to the pilot, and a malfunction is indicated on the NiXie bulb for each engine where oil pressure is less than 50 pounds per square inch. Both of these indications `are analogous to the previous parameter. For engine oil pressure, however, a ymalfunction is also indicated whenever any engines oil pressure is greater than 60 pounds per square inch. A comparison of `an en-gines oil pressure and the upper malfunction limit is performed during the seventh timing period T7. The logical steps for all the computations are set out below in outline form.

Parameter 2 ENGINE OIL PRESSURE b6-Compare SR. A with SR. N looking for A N. I

Shi-ft SR. A around on itself via gate G5 Shift SR. P `around on itself via `gate G dG-Set FFSS if answer to comparison is YES via gate G26 es-Set FP50 for A N 56 on conductor 51 T7 aq-Reset comparator 40 E7 on conductor 46 Load SR. N with Parameter 2 upper malfunction limit from gate G43 in diode memory 12 12T-Compare SR. A with SR. N looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 :J7-Set FF53 if answer to comparison is YES via gate G25 T8 Same as Parameter l.

The .third parameter is oil cooler flap position. For this parameter, the performance section ldetermines which engine has the maximum ap position and indicates the flap position of that engine on .an indicator in the cockpit. There is no malfunction measurements for ap position. This parameter differs from .the previous ones in that the engine having -a maximum flap position is the worst performing while in the previous parameter the engines having Va minimum val-ue were the worst performing. Therefore, at the beginning of the performance sections operations for the first engine, the P register is reset and filled with zeroes by negative going pulses applied from gate G23 vupon the coincidence of a P3, E1 and a1 signals.

There is set down below in outline form the steps carried out by the performance section.

Parameter 3 OIL COOLER FLAP POSITION T1 :t1- Reset comparator 40 El on conductor 46 Load SR. P with Os on engine 1 via gate G23 Set nip-flop Sil for A N via conductor 51 and a gate G24 bl-(Compare SR. A with SR. N. Answer must be YES) Shift contents of SR. P into SR. N via gate G9 Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 dl-(Set flip-flop 53 if answer to comparison is YES) el-Reset llip-iiop 53 and flip-dop 55 el on conductor 54 v T2 zzz-Reset comparator 40 E2 on conductor 46 i12-Compare SR. A with SR. N. looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 dg-Set iiip-op 53 via gate G25 if answer to comparison is YES Same as Parameter 1 Same as Parameter l Same as Parameter l a6-Reset comparator 4t) E5 on conductor 46 [2V-(Compare SR. A with SR. N. Answer must be GNO'S) Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 dG-(Set flip-nop 53 if answer to comparison is LXI'ES) e-Set flip-*flop 50 for A N E6 on conductor 51 aq-Reset comparator 40 57 on conductor 46 b-(Compare SR. A with SR. N. Answer must be GS'YES'5) Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 dq-(Set flip-flop S3 if answer to comparison is YES) :z8-Reset comparator 4t) E8 on conductor 46 Load SR. N with ls by a gate G28 b21-(Compare SR. A with SR. N. Answer must be v No.u)

Shift SR. P around on itself via gate G10 d8-(Set flip-flop 53 if answer to comparison is YES.) f8-(Set flip-flop 55 if flip-flop 53 is set (malfunction indication) via gate G29 Reset ilip-op 50 for A N E8 The fourth parameter is percent revolutions per minute, abbreviated %RPM.

Performance section 10 during time intervals T1, T2, and T3 determines as the worst performance engine that engine which has `the largest %RPM. The parts used, and the logical steps performed are identical to those of the previous parameter as described above.

Performance section 10 determines during timing interval T4, and provides during timing pulse a5, a signal indicating if an engine is revolving at less than 94% RPM. The determination is made as follows; comparator 40 is reset by an E4 pulse on conductor 46, register N is lled with a 94% limit from diode matrix 12 activated by P4 and a4 signals applied to a gate G46. The contents of the A register containing a number proportional to a particular engine %RPM, and the contents of the N register proportional to the 94% RPM limit are shifted by the b4 pulse train into comparator 40 for comparison. Flipflop 50 has previously been reset by E3 `signal therefor interrogation unit 41 is looking for A (an engines RPM) less than N (94% RPM). A d4 pulse applied to gate G26 synchronizes an output pulse from gate G26, if A is less than N, to set flip-flop 53. If set, ip-op 53 provides a high signal on conductor 76 to a gate G31, that is further partially qualified by a P4 signal. Gate G31 is then fully qualified by an a5 pulse to pass a negative pulse to the performance monitor 14 via conductor 77. This pulse is used in computations of the 8th parameter, turbine inlet temperature.

During the T5 timing period, performance section 10 provides a Prop low warning signal if an engines %RPM is less than 97% and the throttle position is above ight idle CAbFI or at full throttle CAFT. To determine if the throttle is CAbFI or CAFT, performance monitor 14, through a conductor 108 provides a K4 signal, indicating that the throttle is in either the CAbFI or CAFT position, to a gate G47 in diode memory 12. Gate G47 also received P5 and a5 timing signals, and when the signals coincide, a signal proportional to 97% RPM is gated into the N register.

Performance Isection in response to the b5 pulse compares the number in the A register (proportional to the %RPM of an engine) with number in the N register, the 97% limit. Interrogation subunit 41 has been set by the d3 signal to look for A less than N. If A is less than N, dip-flop 53 is set via d5 signal to gate G26 providing a FFS high signal to the prop low RPM energizing block 90,'shown in detail in the schematic drawing of FIGURE l1. Block 90 illuminates, as appropriate, lights in the cockpit labeled Prop low engine l, Prop low engine 2 etc.

Block 90 includes a first Nand gate G90 that receives the P5, a5 and FFS signals, and a'group of four Nand gates G91 through G94 that areenergized by an output from gate G90, timing signal T6, and each respectively by engine signals E1 through E4. Gates G91 through G94 have outputs connected respectively to set S inputs v of four flip-flops 111 through 114. Set output S from During time intervals T6 and T7, the performance section compares an engines performanceto variable lower and upper malfunction limits and provides a malfunction signal to illuminate a .NiXie bulb in accordance with those engines whose %RPM is outside of these limits. `The variable upper and lower limits are deter- 1 14 closed at full throttle, CAFT. Each of these throttle positions provides one or more of four command signals designated K2 through K4 and the relationship between the throttle position and signals is as follows. For throttle position CBFI, K2 is high and K3, K4, and K5 are low. For throttle position CAtFI, K3 is high and all the other signals are low. For throttle position CAbFI, the K3 and K4 signals are high and the K2 and K5 signals are low. For throttle position CAFT, the K3, K4, and K5 signals are high and the K2 signal is low. Both the K2 through KS signals as well as their inverses 'fi-2 through are used.

Reference 4is now made to the schematic drawing of performance monitor 14, shown in FIGURE 10 and particularly to the lower portion of the drawing where there is shown the output signal relating to %RPM.

The requirements on the indicator system are that when the throttle position is closed below ight idle, CBFI, the lower malfunction limit is RPM and the upper malfunction limit is RPM, and for any other throttle position, the lower malfunction limit is 98% RPM and the upper malfunction limit-is 102% RPM.

When the throttle is closed below flight idle, a K2 signal is high and the signal is low. K2 signal is applied in performance monitor 14 on a conductor 102 which connects to'gates G48 and G49 in diode memory 12 half qualifying'the gates. Thus when gate G48 receives timing signals a6, a number proportional to 95% RPM is enabled into the N register, 'and when gate G49 receives timing signal a7, a number proportional to 100% RPM is enabled into the N register.

When the throttle position is other than at closed below Iflight idle, K2 signal -is low, and K 2 signal is high. A K2 signal available on conductor 102 is converted to K2 by inverter 104, and the 'K Z signal is applied via conductor `106 to gates G50 and G51 in diode memory 12. These gates are partially qualified by the 'K Z signal and are activated respectively by timing signalsfaa and a7 to provide respectively lower and upper malfunction limits of 95 and 102% to the N register.

The operation of performance section 10 during the fourth parameter are set out below in outline form.

Parameter 4 RPM T1 Same as Parameter 3 T2 Same as Parameter 3 T3 Same asParameter 1 T4 I4-Reset comparator 40 E4 on conductor 46 Load SR. N with 94% RPM from gate G46 of diode matrix 12 Reset low Prop RPM flip-Hops 111-114 as appropriate via gates G95-G98 FIGURE 11 b4-Compare SR. A with SR. N looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 d4-Set flip-flop 53 if answer to comparison is YES viagate G26 eg-On engine 4, provide pulse via gate G87 FIGURE 9 to clear output matrix 86 T5 Va5-Reset comparator 40 E5 on conductor 46 Load SR. N with.97% RPM from gate G47 of from performance monitor 14 Deliver 94% Prop RPM pulse to performance monitor`14 if flip-flop 53 is set va gate G31 On engine 4, provide pulseto gate G83 FIGURE 9 to transfer worst case engine information [J5-Compare SR. A with SR. N looking forA N Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 i5-Set iiip-op 53 if answer to comparison is YES vla gate G26 diode memory 12 if qualified by K4 signal' is T6 1G-Reset comparator 40 "s on conductor 46 Load SR. N with P lower malfunction limit from gates G48 or G50 as by performance monitor 14 Set via G90 FIGURE 11 appropriate Prop Low RPM flip-op, if Hip-flop 53 is set lr6- Compare SR. A with SR. N looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G Shift SR. Q around on itself via gate G14 ds-Set flip-flop 53 if answer to comparison is YES eS-Set flip-flop 50 for A N E6 on conductor 51 T7 aff-Reset comparator 40 Tis on conductor 46 Load SR. N with upper malfunction limit G49 or G51 as determined by performance monitor 14 bq-Compare SR. A with SR. N looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 Shift SR. Q around on itself via gate G14 L17-Set p-op 53 if answer to comparison is YES T8 Same as Parameter 1 Performance monitor 14 for this parameter, in addition to determining as a function of throttle position the variable upper and lower malfunction limits, also provides redline limit signals to display panel in the cockpit to indicate unsafe upper and lower limits, and a greenline signal to the display panel in the cockpit to indicate a range of values over which the engines should be operating.

The redline indicator is a two position flag on the %RPM display.` It is usually at the 102% limit but may be driven to the 107% limit when suitably energized. The aircraft is such that it is unsafe to operate the engines at greater than 102% RPM for throttle positions of flight idle and above, CAtFI and above, and it is safe to operate the engines up to 107% RPM at throttle positions below iiight idle CBFI. Performance monitor 14 receives a KZ signal on conductor 102, and when K2 is high, i.e. throttle in below flight idle position, a relay 120 is activated and drives the red flag to the 107% position. When the K2 signal goes low, the relay is opened and the ag returned to its usual position at 102% The greenline indication is also a two position flag located on the %RPM indicator in the cockpit. This ag is usually in the 98.5 to 101.5 range for the throttle positions of at iiight idle and above. It is put in the range of 95 to 100%, when the throttle is in the below flight idle position. The K2 signal available on conductor 102 applied through relay 120 also drives the green iiag to the 95 to 100% range when the K2 signal is high.

The %RPM parameter has the simplest type of variable malfunction limits, variable redline limits, and greenline range markers. These limits are always one of two values; the choice of the two values is a function of only four discrete values, namely one of the four throttle positions. The parameters of fuel ow P6 and turbine inlet temperature TS are more complicated in that the malfunction limits are not one of two discrete values but are continuously variable, taking any value over a range and in addition to being a function of the four throttle positions, are also functions of air data variables that are continuously variable over a range of values. To complicate matters, these malfunction limits for these parameters are nonanalytic and nonlinear functions. Therefore, a look-up memory is used, and in optical memory 16, the tables of the variable functions are stored.

The fifth parameter is oil temperature and the operation of performance section 10 for this parameter is similar to the operations previously described, and may be traced with the aid of the following outline and notes appended thereto. It should be noted there is a fixed lower malfunction limit of 65 C., but a variable uppermalfunction limit of 85 or 100 C. The appropriate upper limit is selected by the performance monitor 14 as a function of throttle position, temperature, and elapsed time.

Parameter 5 orL TEMPERATURE' Same as Parameter 4 Same as Parameter 4 Same as Parameter 1 T4 Same as Parameter 1 T5 Same as Parameter 1 T6 :1s-Reset comparator 40 E6 on conductor 46 Load SR. N with Para. 6 lower malfunction limit from gate G52 of diode memory 12 lr6-Compare SR. A with SR. N looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 Shift SR. Q around on itself via gate G14 d-Set flip-flop 53 via gate G26 if answer to comparison is YES e-Set flip-op 50 for A N 56 on conductor 51 T7 arr-Reset comparator 40 Eq on conductor 46 Load SR. N with Parameter 6 upper malfunction limit from gate G53 or G54 of diode memory 12 and as determined by performance monitor 14 bi1-Compare SR. A with SR. N looking for A N.

Shift SR. A around on itself via gate G5 Shift SR. P around on itself via gate G10 Shift SR. Q around on itself via gate G14 dq-Set flip-flop 53 if answer to comparison is YES via gate G25 erlf A N is high signal on conductor 48, deliver C. hi) pulse (negative) to performance monitor T8 Same as Parameter 1 The upper malfunction limits (see step a7) are defined as follows: The limit is usually 85 C. however, when the throttle is in the CBFI position and the temperature is above 85 C., the limit changes to 100 C. for 30 minutes, and after 30 minutes returns to 85 C. and stays at 85 C. until the throttle is changed to a new position. Also, when the throttle is in either the CAIFI or CAbFl position and the temperature is above 85 C., the limit changes to C. for 5 minutes, and after 5 minutes returns to 85 C., and stays at 85 C. until the throttle position is changed. Finally, when the throttle is CAFT, the limit is always 85 C.

If an engines oil temperature exceeds 85, there is provided after the bq pulse train a high signal from comparator 40 on conductor 48. The high signal is transferred via conductor 49 to a Nand gate G100, that, when also energized by timing signals P5 and e7, transfers through inverter 107 a negative pulse to performance monitor 14.

In performance monitor 14, a iiip-op is set at the beginning of the oil temperature parameter, by a P5 signal applied to its S input, and is reset during the oil temperature parameter computation by the negative 85 C. pulse from gate G100 and inverter 107 applied to its reset R terminal.

Flip-tiop 130 provides a high on output R when an engines oil temperature is greater than 85, and a high on output S when all the engines have oil temperatures less than 85 C. Output S' is connected by a conductor 131 to gate G53 of diode memory. When gate G53 is activated at a signal from S and timing signal P5 and a7, the 85 C. upper malfunction limit is applied to the N register.

The other output R of flip-flop 130 is applied as one input to an AND gate 135. This AND gate and other AND gates used in this system are characterized as follows: When all inputs are high, the output is high, and when any input is low, the output is low. AND gate 

1. A SYSTEM FOR COMPARING A PERFORMANCE PARAMETER OF SEVERAL DEVICES AND DISPLAYING THE PERFORMANCE PARAMETER OF THE WORST PERFORMING DEVICE, COMPRISING MEANS FOR PROVIDING A DIGITAL SIGNAL FOR EACH DEVICE CORRESPONDING TO THE PARAMETER, PERFORMANCE MEANS CONNECTED TO THE SIGNAL MEANS AND INCLUDING MEANS FOR SEQUENTIALLY 